Epoxy based anti-corrosion coatings are widely used for the protection of metal and concrete substrates. Since the future of anti-corrosion coatings will be strongly influenced by environmental legislation and economic constraints, low VOC coating system attract more and greater attention from both paint producers and end customers. In addition, it is the trend that the biomass resources will replace petrochemical products in anti-corrosion coatings to gradually increase sustainability.
In this respect, one approach to achieve low VOC coating is to prepare high solids content coating with reduced solvent addition using low viscosity epoxy. For example, BE-501 (commercial product of Chang Chun Plastics Co., Inc. of Taiwan (hereinafter “CCP”)) are widely used in anti-corrosion coatings. However, since BE-501 is the epoxy resin with solid type, large amount of solvent is demanded to dissolve to dilute such resin. Generally, 25% xylene is mixed with BE-501 and sold as the commercial grade stated “BE-501X75”. Consequently, BE-501 hinders the epoxy resin from low VOC high solid content application.
The coating based on liquid epoxy such as BE-188 (commercial product of CCP) requires less solvent, however, is quite brittle. This is a critical issue for an anti-corrosion coating which requires high flexibility and good adhesion on substrates. Furthermore, the viscosity of the coating composition prepared from liquid epoxy is generally high and thus has poor processability.
Another approach is to include reactive diluents in the composition to significantly reduce the viscosity of the system. However, such diluents also have some disadvantages. For example, the reactive diluents will result in reduced performance properties, such as decreased chemical resistance, decreased impact resistance, decreased water resistance, and reduced corrosion resistance of the resulting coating compositions and articles of manufacture incorporating the same. In addition, the drying time of these compositions is long.
Given the foregoing, it is clear that there is a long-felt need for a coating composition with the properties of low viscosity and rapid curing rate, which exhibit good properties for chemical resistance, impact resistance, water resistance, and corrosion resistance, and which can be formulated from renewable sources.